NEW FEATURES IN CALAMITES AND EQUISETACE A. 289 
form in Eucalamites and Stylocalamites, and in subterranean stems of S. Suckovii 
there is a strict homology. 
The function in both groups was probably the same. The following 
premises, as to the position and function of the short internode, may be 
stated :— 
a. Position, The short internode precedes а new period, 1. e. is situated 
(1) at the base of the stem ; 
(2) between branchless and branch-bearing series ; 
(3) before the strobilus or cone ; 
(4) in Calamarieæ before a combination of (1) and (2). 
b. Function. It bears some relation to height, which is explained by the 
physiological laws of growth as they apply to elongation. Its function 
appears to be to add strength to the stem by the occurrence of two consecutive 
strengthening nodes (with diaphragms) serving the purpose of a double 
support within a short distance. 
EXPLANATION OF THE PLATES. 
PLATE 18. 
Calamites (Calamitina) Schützei, Stur, Middle Coal-measures, Main Coal, Stanton- 
under-Barton, Leicestershire. Exhibiting graphically the hollow pith-cavity of 
Calamites and the periodic occurrence of a short internode. $ nat. size. 
PLATE 19, 
Calamites ( Calamitina) Schützei, Stur, Coal-measures, Brighouse, Yorkshire, 
Exhibiting the regular occurrence of a short internode, as in Plate 18, Circ. 4 nat. size. 
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